The Center for Behavioral Studies in AIDS and substance Abuse will be a coordinated program of outreach, education, and research for persons at risk for Human Immuno-deficiency Virus (HIV) infection and AIDS through parenteral and other forms of illicit drug misuse. San Antonio, Texas the site of the Center, is the tenth largest city in the U. S. with a metropolitan population of 1,185,394. Data from epidemiological studies and other sources suggest the number of injecting drug users (IDUs) in the city is between 15,000 and 20,000. The IDU population is predominantly Hispanic, male, and heterosexual. Seroprevalence studies among IDUs indicate that less than 2% are currently infected with HIV. Thus, this community provides an opportunity and a suitable environment to test the effectiveness of innovative educational interventions in limiting the spread of infection. During a five year period approximately 2,000 illicit drug users will be recruited using street outreach workers and a targeted sampling strategy. The initial assessment will include HIV antibody testing, urine drug screening, the Risk Behavior Assessment questionnaire developed by the National Institute on Drug Abuse (NIDA), a brief acculturation scale, and supplemental instruments developed by a consortium of NIDA projects. Subjects will be randomly assigned to either a standard intervention or an innovative intervention. The innovative intervention will be based on the Indigenous Leader Outreach model developed in Chicago by Weibel and associates. Paraprofessional peer counselors will conduct expanded counseling sessions with content based on principles derived from Social Learning Theory and a mix of contemporary behavior modification principle. Participants will be followed up in a series of monthly home or street contacts which will reinforce the risk reduction messages of the initial counseling sessions. AIDS risk behavior will be re-assessed at 6 and 12 months after enrollment using NIDA-developed follow-up questionnaires and supplemental instruments. HIV antibody testing will be repeated at follow-up. Descriptive, bivariate, and multivariate statistical analyses will be employed to evaluate the effectiveness of each type of intervention. Risk behavior data will be combined with multiple drug abuse indicators to monitor and describe changes in drug-related AIDS risk in the community over time.